The disposal of solid animal excreta present a substantial and increasing ecological provlem. Vast quantities of solid human excreta are processed daily in city and county sewage treating plants by procedures which result in their precipitation and sterilization to form so-called sewage plant cakes. For example, the City of Los Angeles, California produces 150 tons of such cakes per day and Orange County, California 200 tons of such cakes per day. Moreover, the cakes normally are not employed as fertilizer but, instead, are left to pile up in drying areas until they are hauled away and dumped into disposal pits and the like.
Similarly, in California alone 1 million tons of solid cattle feedlot animal excreta is produced annually, most of which is merely piled up to dry and weather in the sun, forming undesirable, hard-to-handle mounds. Like quantities of solid sheep, hog and other feedlot livestock excreta and of solid poultry excreta also accumulate annually and present a serious disposal problem
Various sanitary problems are involved with accumulation of animal excreta. As an example, it should be noted that it is a common practice to fatten certain livestock and poultry by adding massive dose of synthetic hormones such as diethyl stilbestrol to their diets. Animals so fattened are then held up to two weeks or so until their tissue content of such ingested hormones is reduced to below permissible levels. Such reduction in content of ingested hormones occurs in part by excretion. However, such hormones can be leached from the excreta by water and can pass therein into water supplies later used for drinking purposes. Water sterilization procedures such as chlorination have no appreciable effect on the viability of such hormones so that they may be imbibed with the drinking water, a very undesirable situation.
Accordingly, it would be desirable to provide an effective and economical method of utilizing much of the vast quantities of animal excreta accumulating daily. Preferably, such method should be adaptable for use with solid excreta such as human excreta, livestock excreta and poultry excreta, as well as other applicable solid excreta, and should eliminate sanitation problems such as those referred to above.